Identify the following alkynes as terminal (T), internal/symmetrical (IS), or internal/unsymmetrical (IU).
(a)

Verified step by step guidance

1. Step 1: Understand the classification of alkynes. Terminal alkynes have the triple bond at the end of the carbon chain, with one of the carbons in the triple bond bonded to a hydrogen atom. Internal alkynes have the triple bond between two carbon atoms within the chain. Symmetrical internal alkynes have identical groups attached to both carbons of the triple bond, while unsymmetrical internal alkynes have different groups attached.
2. Step 2: Analyze the given structure. Locate the triple bond in the molecule. In this case, the triple bond is between two carbon atoms within the chain, indicating that it is an internal alkyne.
3. Step 3: Determine if the internal alkyne is symmetrical or unsymmetrical. Examine the groups attached to the two carbons of the triple bond. If the groups are identical, it is symmetrical; if they are different, it is unsymmetrical.
4. Step 4: In the provided structure, the two carbons of the triple bond are attached to different groups. One carbon is bonded to a methyl group, while the other is bonded to a longer chain. This indicates that the alkyne is internal and unsymmetrical.
5. Step 5: Conclude the classification. Based on the analysis, the given alkyne is an internal/unsymmetrical (IU) alkyne.

Key Concepts

Alkynes

Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond. They are unsaturated compounds, which means they have fewer hydrogen atoms than alkanes with the same number of carbon atoms. The general formula for alkynes is CnH2n-2, where n is the number of carbon atoms. Understanding the structure of alkynes is crucial for identifying their types based on their bonding and position of the triple bond.

Terminal vs. Internal Alkynes

Terminal alkynes have the triple bond located at the end of the carbon chain, meaning one end of the molecule is a carbon atom bonded to a hydrogen atom. In contrast, internal alkynes have the triple bond located between two carbon atoms, with no hydrogen atoms directly attached to the carbons involved in the triple bond. This distinction is essential for classifying alkynes as terminal or internal.

Symmetrical vs. Unsymmetrical Internal Alkynes

Internal alkynes can be further classified as symmetrical or unsymmetrical based on the substituents attached to the carbon atoms involved in the triple bond. Symmetrical internal alkynes have identical groups on both sides of the triple bond, while unsymmetrical internal alkynes have different groups attached. This classification affects the physical and chemical properties of the alkynes and is important for their identification.